Method of production of morphologically homogeneous silver bromide-rich table-shaped (111) crystals

摘要

A method is disclosed for preparing an emulsion having grains rich in silver bromide in the presence of gelatin as a protective colloid in a reaction vessel wherein a yield of more than 250 g of precipitated silver nitrate per liter of reaction vessel mixture is attained, wherein at least 70 % of a total projected area of all grains is provided by ä111ü tabular grains having an average aspect ratio of more than 2:1 and an average thickness of from 0.05 up to 0.30 mu m and wherein a ratio by number of procentual amounts of hexagonal tabular grains to triangular tabular crystals present is more than 10:1, said method comprising following steps : preparing in a reaction vessel a gelatinous dispersion medium containing an initial amount of oxidized gelatin corresponding with less than 50 % of a total amount of gelatin used in the said method, and said dispersion medium having a volume of less than 2 liter per 500 g of silver nitrate to be precipitated; precipitating therein silver halide crystal nuclei by double-jet precipitation of an aqueous silver nitrate and an aqueous solution comprising halide ions, wherein less than 10 % by weight of a total amount of silver nitrate used is consumed; adding to said reaction vessel gelatin in an amount of more than 50 % of a total amount of gelatin used in the said method; growing said silver halide crystal nuclei by further precipitation of silver halide by means of double-jet precipitation of an aqueous silver nitrate solution and an aqueous solution comprising halide ions, wherein more than 90 % by weight of a total amount of silver nitrate is consumed, concentrating by ultrafiltration the said reaction mixture volume in the said reaction vessel obtained during precipitation growth steps.